In the waters off the Danish capital, there are three artificial islands1 created as sea forts to protect Copenhagen harbour. Situated about 3km from shore is the largest of the three, Middelgrundsfortet, which is actually the world’s largest sea fort. Middelgrundsfortet was constructed in the late 19th century, with much of the materials coming from the excavations taking place to expand the nearby harbour. With an area of 70,000 sq m it also claims the slightly-technical world record for being the “largest artificial island without abutments”2. The excellent high-res images give us a good look at the various…